The present invention relates to antenna systems, and more particularly to dual-antenna systems.
A variety of dual-transmitter broadcasting formats are under development. Such formats include simultaneous transmission of signals from both satellite transmitters and terrestrial (or land-based) transmitters. Two of such formats those identified by the trademark SIRIUS RADIO and the trademark XM RADIO. Both formats have published transmission specifications. The satellite transmissions cover the vast majority of the geographic broadcast area. The terrestrial transmissions complement the satellite coverage primarily in urban areas where the satellites may be blocked from a receiver by a building.
New antennas for receiving the dual-transmission signals are required, especially for automotive applications. The antennas (e.g. whips and window grids) typically used in the automotive area adequately receive signals from terrestrial transmitters. However, the radiation patterns of monopoles have their best reception at low elevation angles with nulls at the zenith. Therefore, monopoles are incapable of receiving signals from satellite transmitters.